Rocket powered launch vehicles have been used for many years to carry human and non-human payloads into space. Rockets delivered the first humans to the moon, and have launched many satellites into earth orbit, unmanned space probes, and supplies and personnel to the orbiting international space station.
Despite the rapid advances in manned and unmanned space flight, delivering astronauts, satellites, and other payloads to space continues to be an expensive proposition. One reason for this is that most conventional launch vehicles are only used once, and hence are referred to as “expendable launch vehicles” or “ELVs.” The advantages of reusable launch vehicles (RLVs) include the potential of providing low cost access to space.
Although NASA's space shuttle is largely reusable, reconditioning the reusable components is a costly and time consuming process that requires extensive ground based infrastructure. Moreover, the additional shuttle systems required for reentry and landing reduce the payload capability of the shuttle. As commercial pressures increase, the need remains for lower-cost access to space for both human and non-human payloads.